Heat the oil in a heavy pan over medium-high heat and brown the pork on all sides. Remove the pork from the pan and set aside.

Pour off a bit of the oil, reduce the heat slightly & add the sugar to the pan, stirring until it melts and bubbles. Stir until the melted sugar turns a rich caramel brown. Splash in the Shaoxing wine or sherry and bring to a boil.

Return the pork to the pan and add enough water to nearly cover the pork, along with the garlic, ginger, sliced shiitake mushrooms, star anise, chiles and cassia. Bring to a low boil, then turn down the heat until it just simmers and cover tightly. Braise the pork for 1 1/2 hours and add the peeled chestnuts. Continue to cook for about 30 more minutes or until the pork is very tender.

Remove the pork and turn up the heat to reduce the sauce. Cook on high until the sauce is reduced and slightly thickened.

Slice the pork across the grain, arrange on plates and spoon the chestnuts and sauce over the top.